JPH02103133A - Aluminum fin material for heat exchanger - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an aluminum fin material for a heat exchanger made of aluminum or an aluminum alloy. The present invention also relates to an aluminum fin material for heat exchangers that has excellent corrosion resistance, chemical resistance, and formability.

[Prior Art] Aluminum or aluminum alloy, which has excellent lightness, workability, and thermal conductivity, is used for the fin material of the heat exchanger of the evaporator of an air conditioner.

However, during operation of the evaporator, the fin surface becomes below the dew point and condensed water adheres to the fin surface, resulting in problems such as material corrosion and increased ventilation resistance. To solve this problem, fin materials with surface treatment coatings that are corrosion resistant and have an affinity for water have come to be used.

This surface treatment can be carried out after the fins are formed (bost coat method) or on the aluminum plate before the fins are formed (precoat method). From this perspective, the pre-coating method was adopted.

However, in the precoating method, it is necessary to process the coating into a fin shape after coating, so it is required that the coating has good moldability, that the coating does not break during molding, and that the molding tool does not wear out. In addition, since organic solvents such as trichlene and alkaline degreasing agents are used to remove lubricating oil from the fin core during molding after assembly, chemical resistance against these is also required.

To meet these demands, inorganic films such as chromate-treated films, anodized films, and boehmite films have been used to impart corrosion resistance. In addition, we use boehmite film, which is an inorganic film, to impart hydrophilic properties, and a mixed film of inorganic substances such as silica, water glass, alumina, and 6 organic substances,
Organic coatings such as water-soluble acrylic resin are used.

Further, a method of applying a crosslinking reaction product of an organic compound and a 6-unit hardening agent on the inorganic film (Japanese Patent Laid-Open No. 62-105029
) has also been proposed.

However, inorganic coatings such as chromate-treated coatings have excellent corrosion resistance but insufficient hydrophilicity, and boehmite coatings have good hydrophilicity but are poor in chemical resistance. In addition, in order to obtain sufficient corrosion resistance, these inorganic coatings must be thick, which has the problem of accelerating tool wear during fin forming. A treated film in which a substance is mixed with an organic resin has excellent hydrophilicity, but has difficulty in continuous molding and has problems with wear of molding tools.

Organic films such as water-soluble acrylic resins have excellent continuous moldability, but have a problem of poor hydrophilicity.

In addition, a film with good hydrophilicity has poor corrosion resistance because it allows water to pass through it, and a film with good corrosion resistance has poor hydrophilicity because it repels water. It is extremely difficult to obtain these conflicting functions of hydrophilicity and corrosion resistance in a single film, so it is important to obtain a film that is hydrophilic and has excellent corrosion resistance, continuous moldability, and chemical resistance. If so, it would have to be a multilayer film, but
However, the crosslinking reaction product of the organic compound and the organic curing agent coated on the inorganic film was not fully satisfactory, even though it compensated for the drawbacks of both.

[Problems to be Solved by the Invention] Therefore, the purpose of the present invention is to provide a coating that is hydrophilic and has excellent corrosion resistance, continuous formability, and chemical resistance, particularly for coating precoated coatings on heat exchanger fin materials. An object of the present invention is to provide an aluminum fin material for a heat exchanger.

[Means for Solving the Problems] The present inventors have attempted to solve the above problems by applying a chemical coating to aluminum or an aluminum alloy thin plate, and applying a corrosion-resistant composite of a specific composition to the aluminum or aluminum alloy thin plate. It was discovered that it is effective to provide an intermediate layer made of a resin film and further provide a specific hydrophilic organic film, leading to the present invention.

That is, the present invention provides a lower layer consisting of a chemical film on the surface of an aluminum or aluminum alloy thin plate, and (a) a polymer of water-soluble unsaturated carboxylic acids, (
b) an intermediate layer consisting of a corrosion-resistant composite resin film obtained by applying and drying an aqueous solution consisting of a compound selected from the group consisting of a zirconium compound, a titanium compound, a silicon compound, and (c) a fluoride; This aluminum fin material for heat exchange and dexterity is characterized by having a composite film composed of an upper layer made of a hydrophilic organic film made of a reaction product of a water-soluble cellulose resin and a water-soluble acrylic resin.

The aluminum or aluminum alloy thin plate used in the present invention is used as an aluminum fin material.

The chemical film formed on the surface of this aluminum or aluminum alloy thin plate is preferably a chromate film such as a phosphoric acid chromate film or a chromic acid chromate film, but a boehmite film, an anodized film, a water glass treated film or a zirconium treated film may also be used. be able to.

In the present invention, the corrosion-resistant composite resin film constituting the middle 11 layer is formed by coating and drying an aqueous solution consisting of the above (a), (b) and (c).

Examples of the polymer of water-soluble unsaturated carboxylic acids as component (a) include polymers of (meth)acrylic acid, esters of (meth)acrylic acid, and copolymers of this and other vinyl monomers. and 0.3 to 30 g/
It is desirable to include II.

Examples of the zirconium compound used as component (b) include fluorozirconic acid and its alkali metal salts, zirconium fluoride, zirconium oxide, and ammonium salts of zirconium carbonate. As the titanium compound, fluorotitanic acid and its alkali metal salts, ammonium fluorotitanate, titanium oxide, etc. are used. As the silicon compound, fluorosilicic acid and its alkali metal salt, silicon fluoride, silicon oxide, etc. are used, and (b
) component is preferably contained in an amount of 0.1 to 15 g151 in the aqueous solution.

Examples of the fluoride of component (c) include hydrofluoric acid, potassium hydrofluoride, and sodium hydrofluoride. Component (c) is in an aqueous solution of 0.05 to 1
It is desirable that og/i be included.

These intermediate layer forming liquids may be applied onto the chemical film by any method such as roll method, dipping method, spray method, etc. After coating 6i, it is dried at 80 to 200°C for 1 to 60 seconds to form the intermediate layer. do.

In the present invention, the hydrophilic organic film constituting the upper layer is composed of a water-soluble cellulose resin and a water-soluble acrylic resin.

As the water-soluble cellulose resin, cellulose, its esters or ethers, or mixtures thereof can be used.

Water-soluble acrylic resins generally have hydrophilic functional groups such as carboxyl groups, hydroxyl groups, and amino groups in their acrylic polymers, and include (meth)acrylic acid, (meth)acrylic acid ester, and (meth)acrylamide. or copolymers of these unsaturated compounds with each other, or copolymers of these unsaturated compounds with other unsaturated compounds, or by hydrolysis etc., the carboxyl group, hydroxyl group, amino group, etc. Examples include acrylic polymers into which hydrophilic groups have been introduced.

These water-soluble cellulose resins and water-soluble acrylic resins are
Preferably, they are used in a ratio of 1:4 to 4:1.

After coating these mixtures on the intermediate layer, 200~
The upper layer is formed by baking at 280° C. for 5 to 60 seconds.

[Function] According to the present invention, corrosion resistance is imparted by a chemical film such as a chromate film on the surface of an aluminum or aluminum alloy thin plate.

In addition, the corrosion-resistant composite resin corrugated film of the intermediate layer is formed in such a way that a chemical film is uniformly covered with a film made of a polymer through a crosslinking reaction between a polymer of unsaturated carboxylic acid and a zirconium compound, and is particularly Due to the action of fluoride, which exists in free form in the intermediate layer, a 6-organic/inorganic film is effectively and firmly formed in the defective areas of the chemical film, and corrosion resistance can be greatly improved.

Zirconium compounds and the like, which are inorganic substances, undergo a crosslinking reaction with organic compounds and exist as part of the reaction product. Furthermore, due to the effect of improving the corrosion resistance of this film, the underlying chemical film can be kept thin, eliminating the problem of wear of forming tools.

In addition, the unsaturated carboxylic acid polymer has very good adhesion with the upper layer, so the chemical resistance of the hydrophilic layer is improved.
Continuous moldability is improved. Therefore, the film can be made thinner, and manufacturing costs can be reduced.

The corrosion-resistant composite resin film of this intermediate layer has excellent corrosion resistance even if it is a very thin film, and its thickness is 0.5 to 5005g1112,
Preferably 3 to 100 B/g+". This is 0
．． If it is less than 5sg/a+2, there is no effect of improving corrosion resistance;
Even if it exceeds 00 ag/m', the effect of improving corrosion resistance is slight, and the manufacturing cost also increases.

The first component of the hydrophilic organic film is water-soluble cellulose, and since the cellulose resin has a large number of hydroxyl groups, it has excellent hydrophilicity.

Chemical resistance can also be improved by mixing and reacting water-soluble acrylic resins. Also, since it is a completely organic film, there is no need to worry about wear of the molding tool.

The thickness of the hydrophilic organic film is preferably 0.05 to Ig/■2. This is because if it is less than 0.05 g/s', the effect of improving hydrophilicity is small, and even if it exceeds Ig/+g2, the effect of improving hydrophilicity is slight, and the manufacturing cost also increases.

[Example] The present invention will be explained in more detail with reference to Examples below.

Example thickness is 0. 1ha of industrial pure aluminum (JISAllo
The o-H2S) strip was degreased and cleaned using a commercially available weak alkaline degreaser. Next, it was immersed in a phosphoric acid chromate-based chemical bath liquid (trade name: Allozin 401/45, manufactured by Nippon Paint Shitsuya) to form a corrosion-resistant chemical film consisting of a phosphoric acid chromate film, and then washed with water and dried. Next, an intermediate layer forming liquid having the formulation shown in Table 1 was applied onto this chemical film using a roll coater, and dried in a hot air drying oven at a temperature of 120°C for 20 seconds to obtain the film thicknesses shown in Table 1. A corrosion-resistant composite resin film was obtained. Next, a paint consisting of a water-soluble cellulose resin and a water-soluble acrylic resin was applied onto the corrosion-resistant composite resin film using a roll coater, and baked in a hot air drying oven at a temperature of 250°C for 20 seconds to form the coating shown in Table 1. Organic hydrophilic films of various thicknesses were formed.

Characteristics (
The results are shown in Table 1.

Here, one cycle of hydrophilicity is a combination of immersion in water at room temperature for 2 minutes and then drying with cold air for 6 minutes, and 50
After 0 cycles, the contact angle with water was measured and evaluated. ◎ is very good (contact angle 20" or less), o is good (contact angle 20@~40"), × is poor (contact angle over 4G")
And so.

Corrosion resistance was determined by observing the surface condition of the fins after 500 hours of a salt spray test. ◎ indicates very good quality, 0 indicates good quality, and × indicates poor quality.

Chemical resistance (1) was evaluated by immersing the sample in commercially available Pressura for 24 hours, then washing with trichlene, and determining the contact angle with water at 1 11J. ◎ is very good (contact angle !5@ or less), 0 is good (contact angle 15" ~ 30@), × is poor (contact angle 30")
(exceeded). Chemical resistance (2) was evaluated by immersing the film in a commercially available alkaline degreasing solution at 50'C for 1 minute and determining the film thickness reduction rate from the film thickness before and after immersion. ◎ is very good (reduction rate 20
% or less), o is good (reduction rate 40% or less), X is poor (
(reduction rate of over 40%).

Continuous formability was determined by continuous 100,000 punches. After the fin press, the wear condition of the forming tool and the appearance of the fin after forming were observed with the naked eye.

Comparative Example A composite wave film having the structure shown in Table 1 was formed on the surface of an aluminum strip in the same manner as in the example. In Comparative Example 8, a water-soluble six-layer resin paint mixed with silica was applied and baked on the chemical film to form an organic/inorganic/mixed film. In comparison IQ, a water-soluble acrylic resin paint was applied/baked on the chemical film to obtain an organic hydrophilic film. Each film thickness is 1
．． It was 5 g/s'.

The properties of the obtained film were investigated in the same manner as in the Examples, and the results are shown in Table 1.

[Effects of the Invention] As explained above, the aluminum fin material according to the structure of the present invention has hydrophilicity, corrosion resistance, continuous formability,
It also has excellent chemical resistance and is very useful for heat exchangers. Furthermore, since the surface treatment film of the present invention is a very thin film as a whole, it is possible to suppress an increase in heat transfer resistance due to the film, and also to reduce manufacturing costs.

Patent applicant: Sumitomo Light Metal Industries, Ltd. Agent Patent Attorney Hidetake Komatsu Agent Patent Attorney Hiroshi Asahi

Claims (1)

[Scope of Claims] A lower layer consisting of a chemical film on the surface of an aluminum or aluminum alloy thin plate, and on the chemical film (a) a polymer of water-soluble unsaturated carboxylic acids, (b) a zirconium compound, a titanium compound, An intermediate layer consisting of a corrosion-resistant composite resin film obtained by coating and drying an aqueous solution consisting of a compound selected from the group consisting of silicon compounds and (c) a fluoride, and a water-soluble cellulose resin and a water-soluble acrylic film on top of the intermediate layer. An aluminum fin material for a heat exchanger, characterized in that it has a composite film composed of an upper layer made of a hydrophilic organic film made of a reaction product with a resin.